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TDA4861 Datasheet(PDF) 4 Page - NXP Semiconductors |
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TDA4861 Datasheet(HTML) 4 Page - NXP Semiconductors |
4 / 12 page 1997 Jan 20 4 Philips Semiconductors Product specification Vertical deflection power amplifier for monitors TDA4861 PINNING SYMBOL PIN DESCRIPTION VP1 1 supply voltage 1 INP1 2 input 1 of differential input amplifier INP2 3 input 2 of differential input amplifier VP2 4 supply voltage 2 for vertical output stage V-OUT 5 vertical output SUB 6 substrate FLB 7 flyback generator output VP3 8 flyback supply voltage 3 PCO 9 pulse circuit output Fig.2 Pin configuration. handbook, halfpage TDA4861 MEH360 1 2 3 4 5 6 7 8 9 VP1 VP2 VP3 INP1 INP2 SUB PCO FLB V-OUT FUNCTIONAL DESCRIPTION Differential input amplifier The differential sawtooth input signal (coming from a ramp output of the TDA4850 for example) is fed to the input at pins 2 and 3. The non-inverted signal is attached to pin 3. The vertical feedback signal is superimposed on the inverted input signal on pin 2. Vertical shift is applied at the inputs in a power-less way (see Fig.1). Flyback generator Signals for the flyback generator and the pulse circuit are generated in the flyback driver stage. The flyback output consists of a Darlington transistor and a flyback diode. The flyback generator can operate in two modes: 1. An external supply voltage is applied for the short flyback time, thus the power dissipation is minimum (see Fig.1). 2. The flyback voltage is generated by doubling the supply voltage (see Fig.5). The 100 µF capacitor C2 connected between pins 4 and 7 is charged up to VP1 during scan, using the external diode and the resistor R2. The cathode of the capacitor C2 is connected to the positive rail during flyback. Thus, the flyback voltage is twice the supply voltage. Vertical output The vertical output stage is a quasi-complementary class-B amplifier with a high linearity. The output contains SOAR (short-circuit protection) and thermal protection. The output current on pin 5 is reduced for a short time (to let the temperature decrease to Tj < 150 °C), when the junction temperature (Tj) exceeds 160 °C. Deflection GUARD Pin 9 will go HIGH if the junction temperature goes too high (see Fig.3). A pulse signal with 50% duty cycle is output on pin 9, if the deflection coil is open-circuit. A flyback pulse signal is output at normal conditions. Further watching can be achieved by means of an external GUARD circuit as shown in Fig.4. The 22 µF capacitor is charged during flyback time (V5 >V8) at normal conditions. In the event of failures, the capacitor is discharged and the GUARD output goes HIGH. GUARD output level (see Fig.4): • LOW for normal conditions • HIGH for deflection coil short-circuit respectively open-circuit • HIGH when there are neither input or output signals. |
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